Cursor

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The cursor project is an ElN project done at the end of the first semester. It consists in driving a DC motor which moves the cursor chariot with the help of a screw.

Cursor in Action

Specification

The basic specification is the following one:

  • On reset, the cursor moves to the start position given by a Hall sensor close to the DC motor.
  • When pos 1 button is pressed, the cursor has to accelerate towards position 1, advance with full speed, decelerate and stop at position 1, be it from the start position or from position 2.
  • When pos 2 button is pressed, the cursor has to accelerate towards position 2, advance with full speed, decelerate and stop at position 2.

The acceleration and deceleration ramps are a function of the position and not of the time. Indeed, it would be very difficult to know when to start decelerating to reach one of the positions if the deceleration was to be produced by a counter. The slope of the ramp has to be chosen such as the acceleration and deceleration distances are in the order of magnitude of 1 cm.

The positions to reach are:

  • position 1 = 8 cm
  • position 2 = 12 cm

The following figure represents the shape of the speed versus position:

Position Range Diagram

Components

The system consists of

Motor control circuit

The chariot DC motor is powered with 12 V. The power circuit contains an H-bridge controlled by digital signals. On the power board, a 5 V regulator generates the proper voltage for powering the FPGA board.

DC motor

The DC motor is controlled by a L6207 H-bridge driver.

Encoder

The angle of the screw can be measured with the help of an incremental encoder module. The model used on the assembly is a AEDB-9140-A12, which has 500 Counts Per Revolution (CPR).

Hall sensors

The hall sensor is a switch which is working with the hall effect. If a magnet is close to the sensor, the contact closes. For the projects 2 hall sensors are used to identify the left and right limits of the chariot.

FPGA board

The main board is called FPGA-EBS and is a the school main development board. It features many different connectivity and a Xilinx FPGA Spartan xc3s500e.

For additional information see the UIT Wiki

Buttons and LEDs

The Button and Led parallelboard can be attached to the FPGA-EBS and has 4 additional buttons and 8 additional leds which you can use.

Getting started

In order to start the projects you should do the following:

Additional Information

Additional informations for Professor

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